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inkyvoyd
 2 years ago
Best ResponseYou've already chosen the best response.0if y=3x^2+2x and dx/dt=4, find dy/dt when x=3 My answer: dy/dt=24x+8; dy/dt=80. Can someone please check this? THanks!

tamtoan
 2 years ago
Best ResponseYou've already chosen the best response.0isn't it dy/dt = 6x dx/dt + 2dx/dt ? can someone check this ?

zepdrix
 2 years ago
Best ResponseYou've already chosen the best response.2Yah @tamtoan is on the right track there,\[\huge y=3x^2+2x\]If we take the derivative with respect to TIME, we'll get,\[\huge \color{#CC0033}{\frac{dy}{dt}}=6x\color{#F35633}{\frac{dx}{dt}}+2\color{#F35633}{\frac{dx}{dt}}\]And they gave us information about dx/dt and x.\[\huge \color{#CC0033}{\frac{dy}{dt}}=6(3)(\color{#F35633}{4})+2(\color{#F35633}{4})\]Understand where those numbers are coming from?

inkyvoyd
 2 years ago
Best ResponseYou've already chosen the best response.0Uh, the answer is defienitely 80, because I just submitted te assignment. Let me go over what happened though

inkyvoyd
 2 years ago
Best ResponseYou've already chosen the best response.0Yeah, @zepdrix , you have the dx/dt because x is a function of t; @tamtoan didn't have that. Thanks.

zepdrix
 2 years ago
Best ResponseYou've already chosen the best response.2Tam had the same thing, he just didn't plug in the x and dx/dt values for you :D

inkyvoyd
 2 years ago
Best ResponseYou've already chosen the best response.0Oh he did :S. Well, thanks for helping out!
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